Electrical signaling apparatus.



No. 683,872. Patented Oct. I, I901. A. U. ALCOCK.

ELECTRICAL SIGNALING APPARATUS.

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A. U. ALCOCK.

ELECTRICAL SIGNALING APPARATUS.

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No. 683,872. Patented Oct. l, l90l. A. U. ALCUCK.

ELECTRICAL SIGNALING APPARATUS.

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ELECTRICAL SIGNALING APPARATUS.

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Patented Oct. I, l90l. A. U. ALCOCK.

ELECTRICAL SIGNALING APPARATUS.

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ELECTRICAL SIGNALING APPARATUS.

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Patented Oct. I, l90l. A. U. ALCOCK.

ELECTRICAL SIGNALING APPARATUS.

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ELECTRICAL SIGNALING APPARATUS.

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A. U. ALCOCK. ELECTRICAL SIBNALING APPARATUS.

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No. 683,872. Patented Oct. l90l. A. U. ALC'OCK.

ELECTRICAL SIGNALING APPARATUS.

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No. 683,872. Patantad Oct. I, l90l. A. U. ALCOCK.

ELECTRICAL SIGNALING APPARATUS.

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Clktorngy No. 683,872. Patented Oct. l90l.

A. U. ALCOCK.

ELECTRICAL SIGNALING APPARATUS.

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ELECTRICAL SIGNALING APPARATUS.

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ELECTRICAL SiGNALING APPARATUS.

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ALFRED UPTON ALCOCK, 01? LONDON, ENGLAND.

ELECTRICAL SIGNALING APPARATUS.

SPECIFICATIPN forming part Of Letters Patent NO. 683,872, dated octbei 1, 1901. Application filed January 31, 1901. Serial No. 45,411. (No model.)

To all whom, it may concern.-

Be it known that I, ALFRED UPTON AL- COOK, a subject of the Queen of Great Britain and Ireland, residing at London, England, have invented Improvements in or Belating to Electrical Signaling Apparatus, of which the following is a specification.

This invention relates to various improvements in electrical signaling apparatus of the kind in which the transmitting and receiving instruments are connected by three line-wires and the indicator of the receiving instrument or of each of such instruments, where there are two or more, is caused to move in a corresponding manner to the indicator or fother movable part of the transmitting instrument by means of an electric motor, the magnetic field of which is caused to turn or rotate by the action of a commutator forming part of or connected to the transmitting instrument.

The present invention consists in various novel features of construction and combinations and arrangements of parts, all as hereinafter fully described, and pointed out in the claims.

In the accompanyingillustrative drawings, Figure 1 is a diagram showing one arrangement of electrical signaling apparatus according to my present invention. Figs. 1, 1 and 1 are diagrams showing the working of the apparatus. Figs. 2 and 3 are elevations at rightangles to one another, showing one construction of automatic switch. Fig. 41 is a diagram showing a modified arrangement of the signaling apparatus. Fig. 5 is a developed plan view showing part of the transmitter-case. Fig. 6 is a front elevation, and Fig. 7 a section, on the line A A of Fig. 6, showing one construction of receiving instrument according to this invention. Figs. 8 and 9 are similar views to Figs. 6 and 7, showing a modified construction of receiving instrument. Fig. 10 is a similar view to Fig. 7, showing a further modified construction of receiving instrument. Fig. 11 shows, partly in vertical section on the line B B of Fig. 12 and partly in side elevation, and Fig. 12 in front elevation, a transmitting instrument with one construction of commutator according to this invention. Fig. 13 is a rear end elevation, and Fig.- 14 a side elevation,

of the commutator shown in Figs. 11 and 12, but drawn to a larger scale, and Fig. 15 is a developed view of the commutator-contacts with insulated segments. Fig. 16 is a diagram showing how the commutator-brushes of the commutator shown in Figs. 11 to 15, inclusive, are preferably connected to an electric battery. Figs. 17, 18, 19, and 20 are diagrams illustrating the operation of the commutator shown in Figs. 11 to 15, inclusive.

In the arrangement of signaling apparatus shown in Fig. 1 the transmitting instrument at a is normally disconnected from the linewires 0, d, and 2, leading to the receiving instrument at b, but is adapted on being operated to send a signal to become automatically connected to the said linewvires by a switch at f, provided with a movable indicator which becomes deflected at this time to indicate that a signal has been sent. The receiving instrument at b is provided with a relay at h, adapted on a signal being sent by the transmittinginstrument to close a local circuit 1 and operate a sounding device m. The said receiving instrument is also provided with a short-circuiting device at 77/, whereby the three line-wires c, d, and 6 can be short-circuited upon themselves, so as to cause the switch atf to disconnect the trans mitting instrument at a from the line-wires and at the same time cause the switch-indicator g to return to its normal position. The arrangement is such that upon operating the transmitting instrument at a to send a signal the automatic switch at fwill connect the line-wires c, d, and c to the transmitting instrument and the switch-indicator Q will be deflected and remain deflected and the sounding device on at the receiving instrument at b will be operated and remain in operation until an attendant short-circuits the said instrument by means of the short-circuiting device at n, whereupon the switch-indicator Q will return to its normal position, thus indieating to the person in charge of the transmitting instrument that the signal has been received, and the switchf will be caused to open the circuit between the transmitting and receiving instruments, and thereby prevent waste of electrical energy, a matter of considerable importance when electric batteries are used as the source of electrical supply,

the pointer of the receiving instrument at 7) remaining opposite the signal last sent until another signal is sent by the transmitting instrument. The switch atf maybe operated to close the circuit between the transmitting and receiving instruments at a and b by an electromagnetic device 19, the circuit of which is adapted to be temporarily closed by the movementof the handle of the transmitting instrument, as hereinafter described, the said circuit between the transmitting and receiving instruments being maintained closed by another electromagnetic device o (brought into action by the closing of the said circuit) until the said circuit is short-circuited, as hereinbefore described. The circuit of the electromagnetic device 10 may be provided with a hand-operated switch r, whereby it can be opened when desired, so as not to be completed when the transmitting instrument is operated.

Apparatus to operate in the manner set forth can be constructed in various forms.

In the arrangement shown in Fig. ,1 the transmitting instrument at a comprises a rotary commutator provided with an operatinghandle t and a pointer u, that is arranged to move over a fixed dial 1:, bearing the orders, signals, or other indications (hereinafter called signals) to be sent. The rotary commutator may be of any suitable kind. In Fig. 1 the commutator comprises two fixed contacts or brushes w as, that are respectively connected by conductors to and 00 to the opposite poles of an electric battery y or other suitable electric generator, and three contacts 1, 2, and 3, that are movable relatively to the fixed contacts to and 00, between which they are mounted to rotate. The movable contacts 1, 2, and 3 in the form of curved metal segments having an. angular length of nearly one hundred and twenty degrees each are fixed near together around a cylindrical block 7 and. are respectively connected by three insulated conductors 1*, 2, and 3 to three insulated collars 4:, 5, and 6, carried by the same spindle 7 the insulating-block 7*. On the collars 4, 5, and 6, respectively, bear three stationary brushes 8, 9, and 10, that are connected to three conductors 11, 12, and 13, respectively, for connection by the automatic switch at f, as hereinafter described, to the three line-wires c, d, and e, respectively, leading to the receiving instrument at b.

This receiving instrument is of a known kind.

It comprises a rotary electric motor having a field-magnet i composed f an iron ring wound with three separate pairs of coils c, d, and e, that are respectively connected at one end of the line-wires c, (l, and e, and the other ends of which are connected together at the point j. The two coils of each pair are arranged in series and diametrically opposite to each other, as shown, and the direction of winding of each pair of coils is arranged to produce opposite poles in the fieldmagnet ring'i at right angles to the pair of coils, andthe three pairs of coils are arranged, as shown, so that their resultant fields are angularly displaced sixty degrees apart around the field-magnet ring 2'.

7c is the armature of the motor, made light and, mounted to rotate within the field-magnet ring 2' and connected to a pointer ar ranged to move over a dial 70 bearing signals corresponding to those on the dial 1; of the transmitting instrument.

The automatic switch at f comprises, as shown in Figs, 2 and 3, three upper coils 1 1, 15, and 16 and three lo'wer coils 1'7, 18, and 19, wound upon separate horizontally-arranged iron cores 20, providedwith polar projections 21, of which there are consequently twelve, arranged in two rows of three each at the front and back of the device. The cores 20 are carried by two side plates f, through which their ends project and between which the several coils 14 to 19, in elusive, are located. Between the two rows of polar projections 21 outside one of the plates f is a pivoted armature 22, and between the two rows of polar projections outside the other plate f is a pivoted armature 23. Each of these armatures normally rests upon an adjustable stop 24, above which is an adjustable contact 25. One of the armature s-viz., 22is permanently connected to the conductor 11 through the coil 17, Fig. 1, and the other armature-viz., 23--is permanentlyconnected to the conductor 12 through the coil 18, the two adjustable contacts 25 above the two armatures 22 and 23 being respectively connected to the line-wires c and d. One of the upper coils-viz., 14-is con nected or adapted to be connected through the hand-operated switch 1", such as a divided socket and plug, to an electric circuit that comprises the battery y and two conductors 26 and 26, and which is adapted to be closed each time the transmitter-handle t, Fig. 1, is operated to senda signal and to be automatically opened when the pointer u of the transmitter is brought opposite a signal on the transmitter-dial v. For this purpose the said handle 15 may be provided with an insulated contact 27, that is connected by means of the conductor 26 through the coil 14 and switch 1" to one pole of the electric battery 'y, the other pole of which is connected through the conductor 26 to a spring-contact arm 28. This spring-contact arm is carried by, but insulated from, the said handle tand is arranged to bear against a ring 29, Figs. 1 and 5, that is fixed to the transmitter-case and is formed with cam-like projections 29 and with intervening recesses 29, which correspond in position to the central portions of the spaces on the order-dial c, that are marked with the orders or signals to be sent. The arrangement is such that when the handle t is turned to send a signal the spring-contact arm 28 will be forced against the insulated contact 27 each time it passes a projection each time it comes opposite a recess 20 -that is to say, when the pointer it comes opposite the central portion of an order on the orderdial t'so that the circuit including the coil 14 will be closed and opened alternately when the handle 6 is operated to send a signal and will be left open when the pointer 1b stops opposite the signal to be sent. One of the other upper coils-viz., -is connected at one end to the line-wire c and at the other end, preferably through a resistance-coil 31, to the line-wire e. The third upper coil 16 is connected at one end to the line-wire d and at the other end, preferably through the said resistance-coil 31, to the said line-wire e. The three lower coils 17, 18, and 19 are arranged to respectively form part of the three separate commutator-conductors 11, 12, and 13, whereof 11 and 12 are connected to the respective armatures 22 and 23, as hereinbefore stated, while 13 is directly connected to the line-wire 2 through the coil 19,

Each of the upper coils 14, 15, and 16 is made with a greater number of turns than each of the lower coils 17, 1S, and 10, so that when the line-wires c, d, and e are not shortcircuited the cores of the upper coils will attract the armatures 22 and 23 with a greater force than the cores of the lower coils and hold them against the contacts 25, whereas when the line-conductors are short-circnited little or no current will pass through the coils 15 and 16 and a larger current will pass through the lower coils 17, 18, and 19, with the result that the cores of these coils will act to pull down the armatures 22 and 23 and so disconnect the commutator-conduetors 11 and 12 from the line-wires o and d. The switch-indicator may consist, as shown in Figs. 1, 2, and 3, of a pivoted pointer g, ar-

ranged to move over a plate or dial 32 and provided with a soft-iron armature 33, arranged in proximity to two of the cores 20 and pole-pieces 21 of the upper coils 15 and 16, Figs. 2 and 3, so as to be operated thereby and move the said pointer over the dial when either or both of the said coils are energized and to be released and allow the said pointer to move back to the zero position when the said coils are short-circuited.

The relay at h for closing the local circuit Z at the receiving instrument at b, Fig. 1, may conveniently comprise three coils 63, that are of considerable resistance and are connected star fashion to the line-wires c, d, and e at c, d, and 6, respectively, and are connected together at 63 and have their cores 64 arranged to attract a pivoted armature 52" and close the local circuit Z through an electric generator 55, a fixed contact 56, and the electric bell m, which is arranged on, in, or near to the said receiving instrument.

The short-circuiting device (shown at n in Fig. 1) comprises three contact-pins 69, carried by a suitable insulating-holder '70 and connected at the points 0, d, and e to the respective lino-wires c, d, and e, and a metal disk or plate 71, that is adapted to be pressed simultaneously into contact with all the said contact-pins 69, so as to short-circuit the said line-wires against the action of a spring 72, which serves to press the said disk or plate 71 when released away from the said contactpins.

The operation of the apparatus is as follows: Immediately upon turning the handle 15 of the transmitter at a to send a signal the circuit of the coil 14 will be completed between the contacts 27 and 28, as hereinbefore described, and the armatures 22 and 23 will be attracted upward against the contacts 25 25 by the core of the said coil, so as to connect the commutator-conductors 11 and 12 to the line conductors c and 62, respectively, and thereby bring the coils 15 and 16 into action by the current shunted therethrough to hold up the said armatures and also bring the coils 63 of the relay h into action to close the local circuit 1 at the receiver, and thereby cause the bell m to ring. As the said handlet is turned, the pointer of the receiver will move in exactly the same manner as the pointer to of the transmitter, so that both pointers at each moment will be opposite similar signals on their respective dials, as is usual in signal-transmitting apparatus of the kind to which this invention relates and as will be readily understood from Figs. 1, 1 and 1, which are diagrammatic views wherein the line N S at right angles to each pair of coils c, d, and e in the receiver at 1) represents the direction of the magnetizing force of that pair of coils when traversed by an electric current. The arrow K, K or K represents the position of the resultant magnetic field of the set of coils c d 6 when traversed by an electric current, and consequently the position of the armature 7c and pointer k of the receiver, and the small arrows as m indicate the direction of the current in the various parts of the circuit for the three difierent positions of the commutator shown in Figs. 1, 1 and 1.

In Fig. l the transmitter is shown disconnected from the receiver and the pointers u and 7c of the two instruments are shown at theirtop positions. Upon turningthe commutator-segments 1,2,and3and the pointeruinto the position shown in Fig. 1 the coil 14 will be temporarily energized and caused to raise the arm atures 22 and 23, which will then connect the commutator-00nductors 11 and 12 to the line conductors c and d, and thereby energize the coil 15 and cause the same to hold up the armatures, as hereinbefore described, the indicator g will be deflected by reason of the armature 33, Fig. 3, being attracted by the core 20 of the said coil 15, the relay-armature 2 will be attracted and complete the local circuitl and cause the bell m to ring, the pair of coils d of the receiving instrument will be cut out of circuit, and the pair of coils 6 connected in series with the pairs of coils 0, so that the resultant magnetic field setup by the current flowing through the two pairs of coils e and 0, when the handle t and pointer Lt have been turned through an angle of thirty degrees, will be also turned through thirty degrees and into the position indicated by the arrow K, which also indicates the position of the pointer ot the receiver. The direction of the current through the various parts of the apparatus in this position of the commutator is indicated by the arrows x. Upon turning the commutator-segments 1, 2, and 3 and pointer u through another angle of thirty degrees-say into the position shown in Fig. 1 the two pairs of coils e and cl will be connected in parallel with one another and in series with the pair of coils 0, so thatthe resultant field (indicated by the arrow K will be moved through another thirty degrees, as also will the armature 76 and pointer 7a, which consequently again corresponds in position to the pointer to of the transmitting instrument. In this position of the commutator current will be shunted through both coil 15 and coil 16. The direction of the current through the various parts of the apparatus in this second position of the commutator is indicated by the arrows 00 If the commutatorsegments 1, 2, and 3 and pointer to be moved through another thirty degreessay into the position shown in Fig. 1-the pair of coils 6 will be cut out and the pair of coils d will be connected up in series with the pair of coils 0, so that the resultant field, (indicated by the arrow K and consequently the armature k and pointer 70, will have been moved through another thirty degrees-that is to say, into a position still corresponding to the pointer a. In this position of the commutator current will also be shunted through the two coils 16 and 15, which will be in series. The course of the current through the various parts of the apparatus in this third position of the commutatoris indicated by the arrows 50 In this way by rotating the commutator (shown in Figs. 1 to 1) through thirty degrees ata time the resultant magnetic field of the coils c d 6' will, as well understood, be caused to take up twelve successive positions located thirty degrees apart and corresponding to twelve different orders or signals on the transmitterdial 1), and the pointer 70' of the receiver will be caused to take up twelve corresponding successive positions over the dial k of the receiver. caused to ring until the three line-wires c, d, and e are short-circuited upon themselves by causing the metal plate 71 of the short-circuiting device to simultaneously bear upon the three pins 69. When this is done, the relay-coils 63 will be short circuited, with the result that the relay-armature 52 will move automatically into its inoperative position and open the local circuit land stop the bell. The receivercoils c, d, and e will also be short-circuited, with the result that the resistance of the circuit through the three line- Wires 0 d e, the commutator-conductors 11,

In each case the hell on. will be esaev 12, and 13, the commutator, and the battery, will be so far reduced that suflicient current will not pass through the coils 15 and 16 to cause their cores to hold up the armatures 22 and 23 against the pulling-down action of the lower cores 20, surrounded by the coils 17, 18, and 19, which, owing to the reduction in the resistance of the circuit, will be energized by a greater current than before. The lower cores and coils will consequently pull down the armatures 22 and 23 and disconnect the line-wires c and d from the transmitter, and the cores of the coils 15 and 16 being then demagnetized the armature 33 of the indicator g will be released and allow the said indicator to return to its zero position, thus indicating that the signal has been received.

In order that the person in charge of the transmitting instrument shall'be certain that the order sent has not only been received but has been correctly understood, means may be provided at the receiving-station b, whereby the short-circuiting of the line conductors c, (I, and e and the opening of the local relaybell circuit Z is prevented until the pointer of an instrument, which Iwill call the reply instrument, having a signal-dial corresponding to that of the transmitting instrument, has been moved opposite to the signal corresponding to that sent. Fig. 4 shows signaltransmitting apparatus of the kind hereinbefore described with reference to Figs. 1 to 1, inclusive, together with a reply instrument for the purpose above mentioned, except as relates to the short-circuiting device shown in Fig. 1, (to. This replyinstrument comprises a controlling a local circuit, including an electromagnetic short circuiting device. The commutator at b is an exact duplicate of that of the transmitting apparatus at a in Fig. 1 and comprises two fixed brushes w and :0 connected to a battery 4 corresponding to that of the battery y at the transmitting-station a, and three rotary segmental contacts 1 2 and 3 that are connected to three commutator-conductors 11", 12, and 13 through fixed contacts 8*, 9 and. 10 and revolving metal rings 4*, 5, and 6 which are connected to the rotary contacts 1, 2 and .5 by conductors 1", 2 and 3". The said electromagnetic device at 19 comprises three, iron cores 75, each wound with two similar coils, one set'of the three coils-viz., 76 76 76"being connected star fashion to the three linewires 0, cl, and 6 between the transmitting and receiving instruments at C6 and b, and the other set of three coilsviz. 77, 77", and 77"-- being also connected star fashion to the commutator-conductors 11, 12, and 13 of the commutator of the reply instrument. As will be seen, the two sets of coils 76, 76, and 76 and 7 7 77 and 7 7 are reversely arranged-that is IIO to say,the common point 76,t0 which the three coils 76, 7G, and 76 are connected, is arranged at the opposite side of the electromagnetic device to that at which the common point 77, to which the three coils 77, 77, and 77 are con nected, is arranged. The electromagnetic device just described is provided with an armature 80, that is adapted to form part of a local circuit 81, including a battery 81, the winding of an electromagnetic short-circuiting device 82, and a hand-operated switch 81, adapted to open and close the said circuit at a second place. The short-circuiting device 82 has an armature 82, that is adapted when attracted to bear simultaneously.upon the three short-circuiting pins 69, connected to the line'wires c d e, and short-circuit such wires, as and for the purpose hereinbet'ore described with reference to Fig. 1. The arrangement is such that normally the local circuit 81 is closed at the place where the armature is located, but open at the place where the hand-operated switch 81 is placed. Upon then sending a signal from the transmitter at (t to the receiver at b the coils 76 76 76 will energize the cores 75, which will attract the armature 80 against the force of gravity or a spring 80 and move it into the open position, so as to make a second break in the local circuit 81. The said armature will remain in the open position until the pointer a of the reply instrument has been moved by the corresponding commutator-handle t into a position corresponding to the signal sent, whereupon, as the commutator of the reply instrument corresponds exactly to that of the transmittinginstrument, thecurrent from the battery y will be caused to pass through the other set of coils 77 77 '77 in the proper order and direction to neutralize the action on the cores 75 of the coils 76 76 76 so that such cores will then be demagnetized and release the said armature 80 and allow it to move into its closed position and close one break in the local circuit. Thus if, for example, when an order has been sent the main-line currentpasses through thecoil76 and returnsthrough thetwo parallelcoils 76and76,asindicated by the arrows at, then when the commutator of the reply instrument has been turned to the required distance to bring the pointer u opposite the corresponding signal on the dial 1; of the reply instrument current will be caused to fiow through the coil 77 and return through the two coils 77 and 77, as indicated by the arrows b; but as the one set of coils is arranged reversely to the other set the current flowing through one set will neutralize that flowing through the other set, and so release the armature 80 and allow it to move into the closed position,as stated. Upon then closing the second break in the local circuit 81 by closing the hand-switch 81 the short-circuiting device 82 will automatically attract its armature 82 and cause the same to bear against the pins 69, thereby shortcircuiting the line conductors c, d, and e,

with the same result as before-viz, of opening the local circuit Z, disconnecting the transmitting instrument from the line conductors 0 (Z c, and allowing the indicator 9 to return to its zero position, thereby indicating that the signal has been properly received and understood.

The receiving instrument at Z) may be of various kinds. Figs. 6 and 7 show one construction of receiving instrument which may advantageously be used. It has a rotary current-motor comprising three pairs of oppositely-arranged field-magnet coils 43, 43, and 43*, corresponding to the pairs ofcoils c, d, and e in Fig.1, the coils having straight iron cores 44 arranged horizontally and parallel to one another in a circular row and an armature consisting of two sector-shaped pieces 45 of iron that are preferably of an angular width of about sixty degrees and are arranged directly facing each other and so as to rotate within the two circular rows of projecting core ends and are fixed to an iron spindle 46, that traverses a fixed polarizing-coil 47, arranged between the armature-segments 45. The spindle is provided with an indicator or pointer 48 and, if necessary, with adjustable weights 49 so arranged as to balance the weight of the armature-sectors 45, so that the armature shall be balanced and free to readily turn to and remain in any position into which it is moved. The armature-spindle 46 may conveniently be mounted in a non-magnetic metal frame 50, that carries the polarizingcoil 47 and is adapted to be inserted in place within the field-magnet 43 44 of the motor and to be fixed to the dial-plate, 51 of the receiving instrument, on which are marked orders or signals corresponding to those on the dial of the transmittinginstrument. The polarizing-coil IIO metal-work 50 of the receiving instrument and a conductor 50",to the armature 52 of the relay at h, Fig. 7, the other end of the polarizing-coil being connected to an insulated pin 53, arranged to bear at one end against an insulated spring-contact 54. This contact is carried by the framework of the motor and is adapted to be connected, as by a conductor 54, to one pole of the battery 55, the other pole of which is connected, through the bell m, to an insulated contact-screw 56, against which the relay-armature 52 is brought when the relay 63 64 is energized, as hereinbefore described. By the construction of receiving instrument described the armature 45 46 and polarizingcoil 47 can be readily inserted within or removed from the field-magnet of the motor without disturbing the latter. Figs. 8 and 9 show another construction of receiving instrument. In this case the six cores 44 of the six field-coils 43 are arranged at an angle to one another in an annular row, so as to form a hexagonal figure, the ad acent ends of the cores 44 being held in place by six grooved rods 58. In this case the armature-sectors 45 are arranged diametrically opposite to each other. In other respects the armature and its polarizing-coil 47 may be arranged as in the construction of receiving instrument shown in Figs. 6 and 7. In each case the armature-spindle 46 should project equally from each end of the polarizing-coil 47 to prevent an end thrust being imparted thereto when the said coil is energized. Also there may be provided inconncction with the armature-spindle in each case a brake device that is operated magnetically to release the spindle when the coil is energized and is applied mechanically to hold the armature in place whenthe receiving instrument is dis connected from the transmitting instrument and the circuit of the polarizing-coil is consequently opened. For this purpose one end of the armature-spindle 46 may, as shown in Fig. 10, be embraced by a brake-strap 59, carried by a spring-blade 60, that 'is provided with an armature 61, arranged opposite a projecting end of a fixed hollow iron core 62, upon which the polarizing-coil 47 is wound and through which the said armature-spindle extends, the arrangement being such that the brake-strap 59 will be moved away from the armature-spindle 46 when-the core 62 is magnetized and applied to the armature-spindle by the spring-blade when the core is demagneiized. In this case the armatures'pindle46 may carry only one armature-sector 45, and the field-magnet cores 44, when t heseare'parallel to one another, as shown, maybe magnetically connected together at one end-as, for example, by an iron ring 44.

Figs. 11 to 15, inclusive, show one construction of commutator according to this invention suitable for transmitting twentyfour different signals. -It comprises two annularly-arranged sets of contacts fixed upon a rotary cylindrical block 83,0f insulating ma terial, that is secured upon a suitably-supported spindle 84, provided with an operating-handle t. One set of contacts, hereinaftercalled the main contacts, comprises, as shown in Figs. 13 and 15, three curved metal segments 85, 86, and 87, that are ofan angular or circumferential length of about one hundred and five degrees each and are separated from one another by segments 88, of insulating material, each having an angular length of about fifteen degrees, the three metal segments 85, 86, and 87 being suitably electrically connected to the three separate line-wires c, e, and d, as hereinafter described. The other set of contacts, hereinafter called the supplementary contacts, comprises, as shown in Figs. 12 and 15,three pairs of short L-shaped metal contacts 90 91, 90 91 and 90 91, the two contacts of each pair being arranged adjacent to but insulated from each other and so as to overlap one another to an angular extent of fifteen degrees and each having an angular length of thirty degrees, the collective angular, length of the two contacts being about forty-five degrees. The three pairs of overlapping supplementary contacts are separated from each other by insulated segments 92, that may be of metal, having an angular length of about seventy-five degrees, Figs. 12 and 15. The overlapping parts of each pair of supplementary contacts are arranged opposite the insulating-segment 88 between two of the adjacent main metal contacts 85, 86, and 87. The adjacent ends of the main contacts and 86 are respectively connected to the supplemen tary contacts 90 and 91 by conductors 93 and 94, as shown in Fig. 15. The adjacent ends of the main contacts 86 and 87 are similarly connected to the supplementary contacts 90 and 91, and the adjacent'ends of the main contacts 87 and 85 are'similarly connected to the supplementary contacts 90 and 91*, respectively. Bearing upon diametrically opposite sides of the commutator, so as to make connection with the main contacts 85, 86, and 87, are two contact-brushes 95 and 96 for connection to the terminals of a battery 1 Fig. 16, corresponding to the battery 'y in Fig. 1, the number of cells in such battery being preferably divisible by four. Bearing upon diametrically opposite sides of the commutator, so as to make connection with the supplementary contacts 90 91, 90 91, and 90 91 are two other contact-brushes 97 and 98, that are to be connected to intermediate parts g g respectively, of the battery y, so that a quarter of the cells will be interposed between each main brush 95 96 and the corresponding supplementary brush 97 98, as shown in Fig. 16, the two brushes at each side of the commutator being arranged in the same plane. (See Fig. 12.) Each supplementary brush 97 and 98 is composed of two spring blades, Figs. 11 and 16, each made of a width adapted to bear upon rather less than one-half of the width of the supplementary contacts and capable of being adjusted end'wise,so that it will not come onto a supplementary contact until the corresponding main brush 95 or 96 has left the main contact to which the said supplementary contact is connected, so as to avoid shortcircuiting the cells located between the pair of main and supplementary brushes. To allow of endwise adjustment, each spring-blade may be formed with a slot 97", through which the fixing-screws 97 extend, Fig. 11.

By the.construction and arrangement described when the compound commutator is connected up, as shown in Fig. 16, to an electric generator and tothe three coils or three pairs ofcoils 0' cl 6, Fig. 1, of a receiving instrument of the kind hereinbefore referredto and caused to make one complete rotation the resultant magnetic field of the three coils ISO or pairs of coils, and consequently the pointer 7c of the receiving instrument, will be caused to take up twenty-four successive positions located fifteen degrees apart and correspond- 

